Localization and habituation of sensory evoked DC responses in cat cortex

Using calomel electrodes and chopper stabilized amplifiers, sensory evoked d-c responses at the cortical surface were recorded from the primary visual, secondary visual, auditory and somatic areas of the left hemisphere in thirty acutely prepared immobilized cats. The stimuli were light from an incandescent bulb, a hissing sound and a mild shock. Responses were quantified on line by automatic computation of area under the response and by waveform averaging. All four cortical loci could respond to all three stimuli, but by an algebraic analysis of response amplitudes the responses could be fractionated into two components, one of which was localized, the other diffuse. The local component is stimulus bound and is distributed such that the response of the classical sensory area relevant to the stimulus is negative to the response of the other sensory areas, regardless of the over-all response polarity. The diffuse component is on the average, negative in polarity and has a longer latency and duration than the local component. It occurs primarily as an aftereffect of stimulation and is more readily evoked by shock and hiss than by light. The diffure component and the local component are, therefore, distinguished from one another both by their localization and their time course. Both the diffuse component and the local component showed considerable habituation during a 1.5 to 2.0 hour long series of fifty stimulations. The responses probably reflect the joint action of both specific and diffuse cortical inputs, but it is unlikely that they influence the production of action potentials in cortical neurons.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33421/1/0000823.pd

Monocular deprivation in adult mice alters visual acuity and single-unit activity

It has been discovered recently that monocular deprivation in young adult mice induces ocular dominance plasticity (ODP). This contradicts the traditional belief that ODP is restricted to a juvenile critical period. However, questions remain. ODP of young adults has been observed only using methods that are indirectly related to vision, and the plasticity of young adults appears diminished in comparison with juveniles. Therefore, we asked whether the newly discovered adult ODP broadly reflects plasticity of visual cortical function and whether it persists into full maturity. Single-unit activity is the standard physiological marker of visual cortical function. Using a more optimized protocol for recording single-units, we find evidence of adult ODP of single-units and show that it is most pronounced in deep cortical layers. Furthermore, using visual evoked potentials (VEP), we find that ODP is equally robust in young adults and mature adults and is observable after just one day of monocular deprivation. Finally, we find that monocular deprivation in adults changes spatial frequency thresholds of the VEP, decreasing the acuity of the deprived pathway and improving the acuity of the non-deprived pathway. Thus, in mice, the primary visual cortex is capable of remarkable adaptation throughout life

A semi-persistent adult ocular dominance plasticity in visual cortex is stabilized by activated CREB

The adult cerebral cortex can adapt to environmental change. Using monocular deprivation as a paradigm, we find that rapid experience-dependent plasticity exists even in the mature primary visual cortex. However, adult cortical plasticity differs from developmental plasticity in two important ways. First, the effect of adult, but not juvenile monocular deprivation is strongly suppressed by administration of barbiturate just prior to recording visual evoked potentials, suggesting that the effect of adult experience can be inactivated acutely. Second, the effect of deprivation is less persistent over time in adults than in juveniles. This correlates with the known decline in CREB function during maturation of the visual cortex. To compensate for this decline in CREB function, we expressed persistently active VP16-CREB and find that it causes adult plasticity to become persistent. These results suggest that in development and adulthood, the regulation of a trans-synaptic signaling pathway controls the adaptive potential of cortical circuits